This invention relates generally to millimeter wavelength antennas, and more particularly to a supported dielectric waveguide frequency scan antenna.
Frequency scan antennas have utility in radar systems such as those required for surveillance, obstacle avoidance and target acquisition. Such antennas are preferably structurally compact, lightweight and simple in design without sacrificing ruggedness.
K. L. Klohn et al in an article entitled "Silicon Waveguide Frequency Scanning Linear Array Antenna" disclose a frequency scan antenna having a dielectric rod of rectangular cross-section. One side of the rod is provided with periodically spaced metal perturbations formed with copper foil. This article was published in the IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-26, No. 10, October 1978.
A somewhat similar millimeter wavelength dielectric antenna is disclosed by T. N. Trinh et al in an article entitled "Horn Image Guide Leaky-Wave Antenna". The antenna in this case is located in a groove in a metal ground plane and is provided with metal flares. This article was published in the 1981 IEEE MTT-S International Microwave Symposium Digest.
The foregoing structures, because they incorporate metal, are subject to transmission conductor loss. Moreover, the correct positioning of the metal strips and the bonding of them present some difficulties.
In an article entitled "E-Band Leaky Wave Antenna Using Dielectric Image Line with Etched Radiating Elements", K. Solbach describes a frequency scanned antenna using a dielectric image line with etched metallic disks on top of the waveguide as the radiating elements. This was published in the 1979 IEEE MTT-S International Microwave Symposium Digest. As indicated above, transmission conductor loss results from this arrangement.
T. Itoh in an article entitled "Leaky-Wave Antenna and Band-Reject Filter for Millimeter-Wave Integrated Circuits" in the IEEE MTT-S International Microwave Symposium Digest, 1977, describes an inverted strip dielectric waveguide. In this structure the guide is mounted above a dielectric strip having periodic grooves. The guiding layer has a dielectric constant of .epsilon.'=3.75.
K. Solbach has published in the IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-29, No. 1, January 1981, an article entitled "Slots in Dielectric Image Lines as Mode Launchers and Circuit Elements". The slots referred to are made in the metal ground plane positioned below the dielectric waveguide.
In U.S. Pat. No. 3,959,794, M. M. Chrepta et al disclose a semiconductor waveguide antenna having parallel and uniformly spaced conductive wires embedded in the radiating surface.
In U.S. Pat. No. 4,092,647, J. J. Borowich et al disclose an antenna with electronic beam scanning having a slotted metal waveguide.
It is therefore an object of this invention to provide a frequency scanned dielectric antenna which avoids the transmission conductor losses resulting from the use of metal strips or wires.
It is also an object of this invention to provide a frequency scanned antenna in which the dielectric waveguide contains the necessary configuration to produce the scanned radiation beam.
It is a further object of this invention to provide a frequency scanned antenna which is uncomplicated in design and rugged in structure.